This invention relates to a magnetic type fuel injection valve, particularly of the type suitable for use with an internal combustion engine, which is opened as an electromagnet is energized by current pulses controlled by electronic control means, to supply to a suction conduit of the engine a fuel pressurized to a predetermined pressure (in the range between 2 and 5 kg/cm.sup.2).
One type of fuel injection valve known in the art widely in use comprises a stationary core magnetized when an electromagnetic coil is energized, a movable core juxtaposed against one end of the stationary core for movement toward the stationary core upon energization of the electromagnetic coil, and a needle valve secured at one end thereof to the movable core for movement in the axial direction with the movable core as a unit.
In the aforesaid type of fuel injection valve, it is known to use a construction wherein one end of the needle valve is threadedly connected to the movable core and the connected portion is secured in place by a bonding agent, to thereby prevent relative rotational movement between the needle valve and the movable core. This construction has the disadvantage that the bonding agent may find its way into a needle valve guide and render the needle valve immovable.
West German Laid-Open Patent Specification (Offenlegungsschrift) No. 2,349,584 discloses a construction in which a needle valve formed at its end with irregularities is inserted in a hole formed in a movable core and then the movable core is compressed radially inwardly to deform the wall of the hole to conform in configuration with the irregularities in the end of the needle valve, thereby forcibly fitting and hence securing the irregular end of the needle valve to the wall of the hole in the movable core. This construction has the disadvantages that when the irregular end of the needle valve is forcedly fitted to the wall of the hole in the movable core, the movable core and the needle valve may not be coaxially arranged, and that repeated actuation of the needle valve may loosen the tight connection between the needle valve and the movable core.